Carry out a second pathologic review on the second set of 400 Sudden Infant Death Syndrome (SIDS) cases enrolled in the NICHD Cooperative Epidemiologic Study of the SIDS Risk Factors and about 200 cases of infants who died of known cause and were used for quality control. The purpose of the second pathologic review is to determine the certainty with wich a case can be classified as death due to SIDS using slides of certain specific target tissues and to describe the relative importance of the death investigation report to the final diagnosis of SIDS.